Evacuated Tubes

Solar Hot Water Evacuated Tubes are a newer technolgy than flat plate collectors and have been widely adopted in Germany and China. They are more efficient than flat plate collectors at harnessing the sun's energy, and come into their own in the cooler months, when there is less sun and more cloudy days.

The extra efficiency is gained because the collector consists of a series of tubes that always face the sun while the vacuum between the two layers of glass acts like double glazing to insulate against heat loss. The evacuated solar tubes have a fully sealed copper pipe in the centre called a heat pipe which contains liquid within that gets superheated so that vapour rises to the top of the pipe. These tips of the heat pipe (that get red hot without water flowing past them) sit inside a heat transfer manifold and transfer their heat into the water circulated from the solar storage tank on the ground below.